Twitter says it has permanently suspended the accounts of Alex Jones and his Infowars website.
It made the move after a number of tweets that violated Twitter’s abusive behaviour policy, the company said.
A number of tech giants, including YouTube and Facebook, deleted the right-wing conspiracy theorist’s content last month, citing hate speech.
The radio host is best known for spreading unsubstantiated allegations about tragic events, including 9/11.
He is currently being sued for defamation by the parents of two children killed in the 2012 Sandy Hook Elementary School shooting, which he has repeatedly claimed was a “giant hoax”. Twenty children under the age of seven and six adults died in the attack.
Twitter said the ban was a result of “new reports of Tweets and videos posted yesterday that violate our abusive behaviour policy, in addition to the accounts’ past violations”.
It did not specify what the violations were.
It added that it does “not typically comment on enforcement actions… against individual accounts”, but was “open about this action given the broad interest in this case”.
Mr Jones mostly uses his Twitter account to share content and videos from InfoWars with his 850,000 followers, and promote conspiracy theories against liberals, Muslims and migrants.